Mr. Nazir, believed to be in his 30s, was based in the western part of the South Waziristan tribal region. He led the Ahmadzai Wazir tribe, and his loyalists regularly joined attacks on American forces across the porous border with Afghanistan. Unlike other Taliban factions, Mr. Nazir’s fighters did not attack Pakistani military or government targets, instead focusing on the war inside Afghanistan. He was believed to have signed a peace pact with the Pakistani military.

Mr. Nazir was allied with Hafiz Gul Bahadur, a leading warlord in North Waziristan. The nonconfrontational posture of the two commanders toward the Pakistani military often led to them being labeled here as “good Taliban.”

Asad Munir, a former Pakistan Army brigadier and the intelligence chief in Peshawar, said the killing of Mr. Nazir could lead to a spurt in violence.

“A dangerous scenario for Pakistani military would be joining of hands of Hafiz Gul Bahadur and Maulvi Nazir supporters with Tehrik-i-Taliban Pakistan.”